MiR-335-5p inhibits cell proliferation, migration and invasion in colorectal cancer through downregulating LDHB

Purpose: Colorectal cancer (CRC) is a common malignancy with high mortality rate worldwide. The advancement of new therapeutic strategies is crucial for the efficient treatment of CRC. Many miRNAs play a central role in the progression of cancer cells. There are still few studies on miR-335-5p and CRC. In this study, the potential of miR-335-5p in CRC development and progression was explored. Methods: The expression level of miR-335-5p in CRC cell lines and tissues was detected by quantitative real-time polymerase chain reaction (qRT-PCR) assay. Cell counting kit-8 (CCK8) assay and colony formation assay were applied for evaluating the ability of cell proliferation. Wound healing assay and Transwell assay were applied for detecting cell migration and invasion ability. Moreover, dual luciferase reporter assay was performed to validate if lactic dehydrogenase B (LDHB) is a downstream target of miR-335-5p. Western blotting was used to estimate the protein expression of LDHB. Results: The expression of miR-335-5p was significantly low in CRC tissues and cells. To investigate the function of miR-335-5p in CRC, two CRC cell lines (HCT-1I6 and SW620) were selected for further experiments. After transfection with mimics and inhibitors to up-regulate or down-regulate miR33.5-5p, it was found that overexpression of miR-335-5p decreased cell proliferation and inhibited migration ability and invasion, while the knockdown of miR-335-5p showed the opposite results. Then, it was validated in dual luciferase reporter assay that LDHB could be a potential directive target gene of miR-335-5p. Moreover, the rescue assay confirmed that miR-335-5p executed its function as a tumor suppressor through targeting LDHB in CRC. Conclusions: The present study demonstrated that miR-335-5p regulates cell proliferation, migration as well as invasion of CRC cells through down-regulating LDHB, and demonstrated that miR-335-5p/LDHB axis may be an underlying therapeutic strategy in CRC.